The present invention relates to an apparatus capable of controlling with high precision the recording and reproduction of signals by plural heads, and more particularly to a recording/reproducing apparatus in which a recording/regenerative integrated circuit with plural magneto resistive heads (hereinafter abbreviated to MR heads) connected thereto can be controlled with high precision. The invention further relates to an apparatus for reproducing digital information signals or the like with MR heads, and more particularly to a rotary magnetic head type apparatus in which bias currents to MR heads mounted on a rotary drum can be appropriately controlled.
An MR head, which can detect magnetic information signals entered from a recording medium, such as a magnetic tape or a magnetic disk, by variations in resistance, requires the supply of a detecting current (sense current). Furthermore, as such variations in resistance have a nonlinear characteristic with respect to the input magnetic field, an MR head also needs a bias current for keeping the operating point in a more linear region. Recently developed MR heads are designed to utilize these currents (hereinafter to be together referred to as bias currents).
Where MR heads are to be used in a rotary head type magnetic recording/reproducing apparatus, a bias current circuit and a preamplifier circuit are mounted on the rotary drum. Therefore, power to drive these circuits needs to be supplied to the rotary drum side, and it is usually transmitted via a rotary transformer or a slip ring (contact). Also, MR head bias current control signals are transmitted to the rotary drum side via the rotary transformer after being converted into A.C. signals, and further rectified on the rotary drum side to be converted into D.C. voltage signals for controlling the MR heads.
A technique to mount MR heads on a rotary drum and control bias currents to determine the operating points of the MR heads is described, e.g. in J-P-A No. 177924/1998. Further, J-P-A No. 105909/1998 discloses a bias current regulating apparatus capable of flowing optimal bias currents to individual MR heads. J-P-A No. 201005/1995 reveals a method by which optimal bias currents are applied to active MR heads at the time of executing each head switching command.